Overview

Distribution

Range Description

USA: mainly California, in two disjunct (sub)populations in northern (Klamath Mts.) and in southern (Sierra Nevada) California. One locality (metapopulation) of the northern (sub)population is just across the state border in Oregon (Lanner 2007).

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Foxtail pine is endemic to California. There is a 300-mile (480-km) gap in the distributions of the 2 subspecies. Southern foxtail pine occurs in the high southern Sierra Nevada of Fresno, Tulare, and Inyo counties. Its distribution lies within Sequoia and Inyo National Forests and Sequoia-Kings Canyon National Park. Highest population concentrations are in Sequoia-Kings Canyon National Park, the center of most research on southern foxtail pine. Northern foxtail pine occurs in the high North Coast and Klamath ranges in Siskiyou, Trinity, Shasta, and Tehama counties. Northern foxtail pine's distribution lies within the Klamath, Shasta, Trinity, and Mendocino National Forests, including the Marble Mountain, Yolla-Bolly-Middle Eel, and Trinity Alps Wilderness Areas [26,39,59,61]. Southern and northern foxtail pines have probably been separated since major upliftings of the Sierra Nevada during the early Pleistocene [8]. Inyo Valley, located between the southern Sierra Nevada and the White Mountains, creates a 20-mile-wide (32-km) gap between southern foxtail and Great Basin bristlecone pine populations [26]. The U.S. Geological Survey provides a distributional map of southern and northern foxtail pines.

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Description

Foxtail pine is a native conifer. It is a low-growing pine, generally 20 to 50 feet (6-15 m) tall, but occasionally reaching 72+ feet (22+ m) in height [39,76]. The champion tree is a northern foxtail pine on the Trinity National Forest that measures 76 feet (23 m) in height, 34 feet (10 m) in spread, and 26.3 feet (8 m) in circumference [2]. Foxtail pine's trunk is usually single-stemmed. Unlike other North American conifers, foxtail pine rarely assumes krummholz form at high elevations; instead, it retains a straight bole [8,10,82,83]. Bark of mature foxtail pine is "exceptionally thick" [8]: nearly as thick as that of ponderosa pine (Pinus ponderosa). Bark thickness measurements of 1.85 inches (4.70 cm) [45] and 2.4 to 3.1 inches (6-8 cm) [8] are reported for mature foxtail pines. Mature tree crowns are 8.5 feet (2.6 m) or less in diameter. Branches are short and thick in diameter [39,76]. Branching habit is sparse in southern foxtail pine [59]; southern foxtail pine also tends to be self-pruning. Northern foxtail pine branches tend to be thicker, and may extend to the ground [6,39,67] (the photos in the Introductory section illustrate this difference). Foxtail is a 5-needle pine. The Balfourianae complex is unique among pines in that about half of their branches originate from within the needle fascicles [24,59]. Needle clusters are thickly set toward the branch ends, resembling foxtails [58]. Needles persist for 5 to 7+ years [64,70]; trees at lower elevations tend to retain needles longer than trees at timberline [64]. Female cones are 2.4 to 7.5 inches (6-19 cm) long, dehiscent, and have tiny prickles. Seeds are small (~0.3 inch (8 mm) long), with detachable seed wings about 3 times longer than the seeds [39,76]. Northern foxtail pines tend to have heavier cones and larger seeds with longer seed wings than southern foxtail pines [66].

Morphological differences between southern foxtail pine, northern foxtail pine, and Great Basin bristlecone pine are slight. Southern foxtail pine has thinner bark that tends to grow in square plates (pictured above right) compared to northern foxtail pine, which has relatively thicker bark that tends to grow in narrow ridges. Southern foxtail pine retains its needles longer than northern foxtail pine [39]. Northern foxtail pine tends to have a fuller crown and suffer from less cambial die-back than southern foxtail pine [59]. Great Basin bristlecone pine is distinguished from foxtail pines by having relatively longer cone prickles (2-6 mm) compared to foxtail pines (<1mm). Distributions of Great Basin, southern foxtail, and northern foxtail pines do not overlap [39,61], so distinguishing among them in the field is easy.

Stand structure: Foxtail pine communities are typically open, with a sparse understory and scattered woody debris. Arid, high-elevation conditions allow woody debris to persist for many years without decaying [44]. In Sequoia-Kings Canyon National Park, southern foxtail pine grows in widely spaced woodlands in its upper elevational range and is often the only tree species. At lower elevations it forms a more dense forest, either in mixed or monospecific stands [10,12,81,82]. The foxtail pine-alpine ecotone is usually abrupt as a result of foxtail pine's inability to form krummholz [63]. Northern foxtail pine communities tend toward greater density then southern foxtail pine communities [82]. In the Klamath Ranges, stand densities of northern foxtail pine communities ranged from a minimum of 51 trees/ha in the Yolla Bolly Mountains to a maximum of 381 trees/ha in the Trinity Mountains [30]. Stand densities of southern foxtail pine communities in Sequoia-Kings Canyon National Park range from 50 trees/ha to 600 trees/ha [30,63,80,82]. Ryerson [82] found a mean stand density of 100 trees/ha on sites across southern foxtail pine's distribution.

Age class: Age class structure within foxtail pine stands appears mixed [30,68]. Few studies have been conducted on age class distributions in foxtail pine. In a study across the Klamath Ranges, Eckert and Sawyer [30] found northern foxtail pines less than 100 years of age were most common (>50% relative density). A few very old trees (around 1,000 years of age) were scattered within all the study sites. In a study across southern foxtail pine's distribution in the Sierra Nevada, Ryerson [82] found most trees were in the 350- to 500-year-old class, followed by trees less than 200 years old, and trees older than 800 years, respectively.

Foxtail pine is a very long-lived conifer, although it does not approach the extreme ages of bristlecone pines. Foxtail pine occurs on wetter sites than bristlecones; consequently, foxtail pines show relatively faster growth, develop heart rot, and die more quickly than bristlecone pines [8]. Foxtail pine has advanced heart rot by 1,000 years of age. The oldest foxtail pine on record (as of 2004) is a 3,400-year-old southern foxtail pine [82]. Northern foxtail pines occur in wetter habitats then southern foxtail pines and are shorter lived, attaining maximum ages of about 1,600 years [30,68,82].

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

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Ecology

Habitat

Sierra Nevada Forests

The Limestone salamander is a highly localized endemic of the Sierra Nevada forests foothills conifned to a limited reach of the Merced River. The Sierra Nevada forests are the forested areas of the Sierra Nevada Mountains, which run northwest to southwest and are approximately 650 kilometers long and 80 km wide. The range achieves its greatest height towards the south, with a number of peaks reaching heights of over 4000 meters. Several large river valleys dissect the western slope with dramatic canyons. The eastern escarpment is much steeper than the western slope, in general.

The Sierra Nevada forests ecoregion harbors one of the most diverse temperate conifer forests on Earth displaying an extraordinary range of habitat types and supporting many unusual species. Fifty percent of California's estimated 7000 species of vascular plants occur in the Sierra Nevada, with 400 Sierra endemics and 200 rare species. The southern section has the highest concentration of species and rare and endemic species, but pockets of rare plants occur throughout the range.

A number of bird species are found in the ecoreion including high level predators that include several large owls, hawks and eagles. Other representative avifauna species present are the Blue-headed vireo (Vireo solitarius); Brown-headed cowbird (Molothrus ater); and the Near Threatened Cassin's finch (Carpodacus cassinii).

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Habitat and Ecology

Pinus balfouriana occurs in the subalpine to alpine zones of the Klamath Mountains (the northern [sub]population) and of the southern Sierra Nevada (the southern [sub]population). In the north it is found at altitudes of between 1,600 m and 2,400 m a.s.l., in the south between 2,900 m and 3,700 m. Stands of this pine are very open and occur on dry, rocky, exposed high slopes and ridges, usually devoid of other significant vegetation. Stands may be pure or mixed with P. albicaulis, sometimes Juniperus occidentalis grows with it, too. Regeneration and growth are extremely slow and stands commonly look as if entirely composed of veteran trees of great age. Regeneration is probably episodal and may be linked with climatic cycles. Unlike its even longer lived 'cousin' P. longaeva, growing only 35-40 km to the east of the Sierra Nevada, little is known about the exact ages of some of the oldest trees, but they are likely to be more than 2000 years old.

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Habitat characteristics

Foxtail pine is adapted to harsh environmental conditions [59,70]. Its long life span, slow growth, and persistent needles are typical of conifer species adapted to stressful habitats [70]. Foxtail pine holds an ecological position between whitebark pine and limber pine: it is less tolerant of cool, short growing seasons than whitebark pine and less tolerant of warm, arid growing conditions than limber pine [44,86]. North of southern foxtail pine's distribution in the Sierra, freezing temperatures occur all year long [82]. Foxtail pine communities are most common on "safe sites," such as ultramafic soils and dry granite fields, that few other conifer species can tolerate [30,59]. Slope varies from gentle to as much as 55% [82,83].

Southern foxtail pine grows on well-drained, decomposed granite and granite boulder fields. Southern foxtail pine does not occur on serpentine or other ultramafic soils, which are rare in the high Sierra Nevada [51,54,82]. It is more common on the drier, eastern side of the Sierra Nevada, while whitebark pine is more common on the west slope [10,82]. Climate in the southern Sierra Nevada is mediterranean, with cold winters and warm, dry summers [67,86]. Annual precipitation on the east slope ranges from 20 to 30 inches (500-750 mm) [13]. Southern foxtail pine occurs from 8,900 to 12,000 feet (2,700-3,700 m) elevation [39]. Tree damage from ice- and sandstorms is common [67]. Highest density of southern foxtail pine occurs on north-facing slopes; least density is on south slopes. Percent slope across southern foxtail pine's range averages less than 33% [82].

Habitat of northern foxtail pine is even more restricted than that of southern foxtail pine. The Klamath Ranges are geologically complex, consisting of steep elevational gradients and a variety of parent rock materials that strongly influence plant community boundaries [51]. Climate is mediterranean, but is strongly moderated by the maritime influence of the nearby Pacific Ocean [67]. Annual precipitation averages from 49 to 60 inches (1,250-1,750 mm) [13]. Northern foxtail pine occurs from 6,900 to 8,200 feet (2,100-2,500 m) elevation [39]. There are relatively few high-elevation peaks in the Klamath Ranges; therefore, northern foxtail pine tends to segregate into small populations on isolated "sky islands" [77]. Substrates on which northern foxtail pine grows include gabbro, granodiorite, limestone, schist, and most commonly, serpentine [51,54,59,86]. Because most associated conifers (except Jeffrey pine) are less tolerant to them, serpentine soils can partially ameliorate the elevational restriction and lower northern foxtail pine's elevational distribution. Northern foxtail pine tends to grow in large, monospecific stands when on serpentine soils. On other substrates it is generally found in small stands (a few hundred trees) on ridge crests, mountain tops, and steep, south- or west-facing slopes [30,68,77,86]. Populations on serpentine soils are more likely to occur on all aspects, including valley bottoms and lake shores [77]. Percent slope ranged from 15-32% on 4 sites in the Klamath Ranges [82].

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

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Plant Response to Fire

Foxtail pine's thick bark helps protect it from damage from surface fires. Sparse, large-diameter branches discourage torching and fire spread. Little is known about foxtail pine's response after the fire has passed. In the 1979 Fire Management Plant for Sequoia-Kings Canyon National Park, Bancroft [10] wrote "Very little research has been conducted on the effect of fire on natural regeneration in subalpine forests." This remains true of foxtail pine and other subalpine forests today. Research is needed on the fire ecology of foxtail pine.

Kiefer [48] found foxtail pine recruitment in Sequoia-Kings Canyon National Park was uneven-aged and did not appear to be correlated with fire history. This was in sharp contrast to associated Sierra lodgepole pine, whose recruitment dated from past fires. Kiefer suggested that climate may play a more important role in foxtail pine recruitment than fire.

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

Fire adaptations: Foxtail pine has many characteristics of a fire survivor [87]. Some of its morphological characteristics are similar to ponderosa pine, a highly fire-adapted species [4]. Like ponderosa pine, foxtail pine is a long-lived tree with a large-diameter bole, thick bark, and large-diameter branches [8,45]. Branches are generally sparse and self-pruning in southern foxtail pine, although thin branching and a self-pruning habit are less common in northern foxtail pine [39,59,67]. Few fire studies on foxtail pine have been conducted; however, Ryerson [82] found mature, fire-scarred southern foxtail pines throughout the tree's distribution. As further evidence of foxtail pine's ability to survive fire, Keifer [48] reported that in the Sierra lodgepole pine-southern foxtail pine ecotone in Sequoia-Kings Canyon National Park, foxtail pines were uneven-aged and showed multiple fire scars, while Sierra lodgepole pines were even-aged and showed no evidence of scarring. More fire history studies are needed on foxtail pine.

Foxtail pine seedlings pioneer on burned sites. The seeds are small, light, and have large wings [39,70,76], suggesting the possibility of foxtail pine seed dispersal onto burns from on- and off-site parent trees. In Sequoia-Kings Canyon National Park, Ryerson [82] found southern foxtail pine seedlings on 2 burned sites. On the 1st burn, seedlings established near 4 lightning-killed, mature trees. On the 2nd burn, foxtail pine seedlings grew in openings created when fire burned across a ridgetop. Further studies are needed on patterns of foxtail pine seed dispersal and seedling establishment after fire.

FIRE REGIMES: Fires are infrequent, and are generally of low severity, in subalpine regions of the southern Sierra Nevada. Scant litter production and discontinuous fuels do not promote fire spread in foxtail pine communities. Fire intensity tends to decrease when lower-elevation fires burn into southern foxtail pine. Fire spread slows; or, fires may extinguish due to lack of fuels [10,20,21,49,65]. Although foxtail pine sites receive more lightning strikes than lower-elevation forests, ignitions are uncommon [102,103]. Rocky, highly dissected foxtail pine habitats rarely sustain large fires. In a fire history study, Keifer [48] found frequent fire in Sierra lodgepole pine, but only occasional fires in southern foxtail pine sites. The National Park Service [101] classifies fire occurrence as "very low" in subalpine conifer zones of Sequoia-King Canyon National Park, with a mean fire-return interval of 187 years and a maximum recorded fire-return interval of 508 years. Caprio and Lineback [21] found southern foxtail and whitebark pine communities of Sequoia-Kings Canyon National Park had the longest return fire intervals of all plant communities in the Park. Estimated area burned in southern foxtail pine communities averaged 145 acres/year (168 ha/yr) with a mean fire-return interval of 187 years. Estimated burn area extended to 153 acres/year (62 ha/year) under the maximum mean fire-return interval of 508 years. Fire scar data from 2 watersheds show few fires in foxtail-whitebark pine communities of Sequoia-Kings Canyon National Park from 1700 to 2000: 7 on north aspects and 3 on south aspects [19]. Differences in fire-return intervals between aspects were not significant [18].

The fire ecology of upper subalpine zones of California is poorly understood [101]. This is particularly true for northern foxtail pine, for which fire ecology and fire regime information are nearly absent. Thornburgh [95] found white fir-mountain hemlock communities of the Marble Mountains, where northern foxtail pine is an associate, experience a regime of mixed low- and moderate-severity fires. Fire effects and postfire recruitment of foxtail pine were not reported. Further documentation and research are needed on the fire ecology of foxtail pine and other subalpine communities of California.

Fuels: Foxtail pine snags and woody debris are highly resinous, and are slow to decay in high-elevation habitats. In Sequoia-Kings Canyon National Park, downed foxtail pines that have been dead for over 1,000 years still retain medium-sized (>0.8-inch (2-cm) diameter) or larger branches [62]. Foxtail pine communities are not typically highly flammable though, because woody fuels are limited and discontinuous [65,91], and litter is sparse [81]. Live fuels are also scant. A 1978 fuel inventory in Sequoia-Kings Canyon National Park showed a mean of 10 tons/acre in foxtail and other subalpine types [10]. Basal area and litter quantity decreased with elevation, although litter quality (N:C ratio) increased with elevation [64]. The live understory is typically sparse in foxtail pine communities. Lloyd and Graumlich [63] found less than 1 plant/mÂ² in southern foxtail pine understories in Sequoia-Kings Canyon National Park. Van Wagtendonk and others [105] reported the following fuelbed characteristics for southern foxtail pine:

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

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Successional Status

Foxtail pine is shade intolerant, requiring open, sunny locations throughout its life cycle [8,9,82,86]. Foxtail pine pioneers on serpentine and high-elevation subalpine sites [30]. It competes poorly on nutrient-rich, mesic, and low-subalpine sites [77,86]. Foxtail pine is generally noninvasive [79]; however, it has extended its distribution into the California red fir zone in times of global cooling [82]. On high-elevation, ultramafic or dry granitic sites, foxtail pine is not threatened by successional replacement by shade-tolerant conifers such as California red fir and mountain hemlock because no other tree is as well adapted to the harsh sites that foxtail pine occupies [14,30]. On more favorable sites, successional replacement of foxtail pine by mountain hemlock and firs may be occurring. Research is needed on successional patterns in foxtail pine communities on mesic, nonserpentine sites.

A resurvey in Sequoia-Kings Canyon National Park showed that in 27 years, southern foxtail pine basal area and cover increased 8% and 16%, respectively. The changes were entirely due to foxtail pine diameter growth; in 27 years there had been no foxtail pine mortality, and no ingrowth of foxtail pine or other tree species, on the study plots [80]. To date (2004), there are no studies of succession in foxtail pine communities following fire, avalanche, or other disturbances. Studies documenting postdisturbance recruitment and succession in foxtail pine communities are needed.

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

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Regeneration Processes

Environmental interactions that foster foxtail pine recruitment are poorly understood. Climate and water balance may be the primary factors driving foxtail pine establishment, with best recruitment during periods of warm, wet winters and cool summer temperatures [33,36,37,62]. Dendrochronologists studying a 3,500-year history of southern foxtail pine recruitment and death rates in Sequoia-Kings Canyon National Park found 2 periods of poor southern foxtail pine recruitment. The 1st was during a drought lasting decades (950-550 years BP); the other was an extended period of below-average temperatures (450-50 years BP). Death rate was relatively stable over the last 1,000 years, averaging about 0.05% per capita. Death appeared to be due to local or endogenous factors except during periods of extreme climate fluctuation. Mortality spiked during the periods of extended drought and extended cold. Overall recruitment rate was slightly higher than death rate, averaging around 0.06% per capita [62,63]. As of this writing (2004), field studies on the seed germination and seedling establishment stages of foxtail pine's life cycle are lacking. Further studies are needed on the regeneration requirements and life cycle of foxtail pine.

Barriers to regeneration: Domestic livestock grazing may adversely affect foxtail pine regeneration in areas where grazing is still practiced. Vankat [106] found southern foxtail pine in Sequoia-Kings Canyon National Park showed a pulse of recruitment from 1890-1895. That period coincides with a period of reduced domestic sheep grazing in the southern Sierra Nevada.

White pine blister rust (Cronartium ribicola) affects the ability of 5-needle pines to reproduce by killing cone-bearing branch tips. An infected northern foxtail pine population on the Klamath National Forest (see Other Management Considerations) shows poor recruitment, although it is uncertain at this time if blister rust is responsible. Levels of blister rust infection in foxtail pine are being monitored [99].

Breeding system: Allozyme surveys show that genetic diversity is low in foxtail pine compared to other pine species. There is more genetic differentiation among than within populations. Interpopulation genetic diversity is particularly pronounced in northern foxtail pine, which tends to have small (300-600 individuals), isolated populations, and restricted between-population gene flow. Natural selection for serpentine tolerance, global warming (see Other Management Considerations, Climate), and genetic drift have likely contributed to northern foxtail pine's low genetic diversity [77].

Seed production: Foxtail pine 1st produces cones at 20 to 50 years of age [52,82]. The cone cycle (development through maturity) takes 5 to 6 years [28]. There is usually a 5- to 6-year interval between large cone crops [52]. Environmental conditions promoting large crops are undocumented (as of 2004).

Seed dispersal: Foxtail pine seed is dispersed by wind [58,59]. How long seed is retained in the cone, and whether it survives fire and disperses from cones onto burns, is poorly documented (as of 2004). Likewise, average range of dispersal for wind-blown foxtail pine seed is unknown, making it difficult to predict the potential for long-range foxtail pine seed dispersal onto burns or other open seedbeds.

Although Clark's nutcrackers disperse bristlecone pine seeds, there have been no sightings of the birds dispersing the smaller seeds of foxtail pine [60,70]. Trees growing from Clark's nutcracker caches often have multiple, genetically distinct stems [58,59]. The typical single-stemmed habit [8,10,82] of foxtail pine suggests that Clark's nutcracker dispersal and caching is unusual. Ryerson [83], however, noted the presence of a few multiple-stemmed trees throughout foxtail pine's distribution, suggesting the possibility of Clark's nutcracker seed dispersal and caching. Genetic identities of multiple-stemmed foxtail pine "individuals" have not been determined. Further investigation is needed on mechanisms of seed dispersal for foxtail pine.

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

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Broad-scale Impacts of Fire

Fire and climate may play an interactive role in determining the California red fir-foxtail pine ecotone. California red firs (Abies magnifica var. magnifica and A. m. var. shastensis) have thicker bark and are more fire-tolerant than most firs [7], but are not as fire-tolerant as foxtail pine. Warming climate and more frequent fires may promote foxtail pine invasions into lower-elevation California red fir communities [82].

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

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Life History and Behavior

Cyclicity

Phenology

Pollen dispersal and pollination of new foxtail pine cones occurs in July and August. Mature cones open and disperse seed in September and October [27,52]. Common garden studies show foxtail and bristlecone pines open their cones later in the season than other North American pine species [25]. Little is known of foxtail pine's seed biology and the phenological development of seedlings. Further work is needed in this area.

IUCN Red List Assessment

Based on comprehensive sampling of specimens held in herbaria in California and elsewhere, and the fact that very few if any stands of this species would have an area of occupancy (AOO) larger than 4 km² an AOO of only 136 km² was calculated. There are two main areas, separated by nearly 500 km, but the northern area has two locations, one with a much smaller subpopulation than the other. Fragmentation and number of locations therefore also fall within the threshold for Endangered; however, the population appears to be stable at present and there is no evidence of past decline within the last few hundred years. Climate change and air pollution (the latter only relevant to the southern subpopulation) are potential threats. It is therefore appropriate to list this species as Near Threatened (almost qualifies for listing under criterion B2ab).

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Trends

Population

The total number of mature trees is not known, but the population is fragmented, first by a gap of nearly 500 km between the northern and southern (sub) populations, and second by the fact that individual stands are (widely) scattered within these two areas. Numbers of trees in each of these stands vary between a few score to many hundreds. Regeneration and growth to maturity are extremely slow in most stands and may be episodic; this means that if little or no regeneration is observed in a stand at present this will not be evidence of decline. A tree that lives for several millennia only needs to produce offspring a few times in that whole period to replace itself and maintain the population.

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Threats

This species may be at risk in the long term from climate change if this is continuing to accelerate, possibly bringing in competitors and/or pathogens it may not be able to cope with. At present, both disjunct populations are well protected within National Parks and National Forest Wilderness Areas and unaffected by long-term effects of fire suppression in forests as the trees usually occur in remote subalpine locations where such measures have not been undertaken. It would be profitable to study the (aut-)ecology of this species in more detail in order to be able to estimate risks under various climate change scenarios. The southern (sub)population in Kings Canyon N.P. and Sequoia N.P. are subject to air pollution from major urban centres such as Los Angeles. The effect, if any, on this species is as yet unknown and needs to be researched.

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Management considerations

Damaging bioagents:Foxtail pine is highly susceptible to white pine blister rust, a usually fatal fungal disease that affects 5-needle pines [40,71,84]. In the greenhouse, Hoff and others [40] inoculated 18 species of Eurasian and North American 5-needle pine seedlings with blister rust. Of the 18 species, foxtail and southwestern white pine (Pinus strobiformis) showed least resistance to blister rust. All of the 92 inoculated foxtail pines became infected. Other studies show a 75-100% seedling infection rate [93]. Although the mediterranean climate of California once protected all but the northernmost populations of 5-needle pines from blister rust, that is no longer true. Some northern foxtail pines on the Scott River District of the Klamath National Forest have blister rust [96,97,99]. As of this writing (2004), blister rust has not been detected in southern foxtail pine, although western white pine and sugar pine (P. lambertiana) in Sequoia-Kings Canyon National Park are infected [84,99].

Blister rust-infected trees may take from 2 years to decades to succumb, but infection is always fatal [41,42].Gooseberries and currants (Ribes spp.) are the primary host of white pine blister rust. Life cycle of white pine blister rust is complex. Gitzendanner and others [35] and McDonald and Hoff [71] provide details of the rust's life history and ecology. Hoff [41] provides a diagnostic guide to aid managers in recognizing symptoms of blister rust infection in white pines. There are no known methods of controlling blister rust [47]. Fungicide application, pruning infected tree branches, and/or removing Ribes spp. have neither eliminated nor controlled white pine blister rust [22,71], and such treatments have undesirable ecological effects [47]. For further information on management of white pine blister rust, see Samman and others [84].

Some northern foxtail pines on the Scott River District show phenological resistance to blister rust. Identification and breeding programs for these genetically valuable, blister-rust resistant individuals are crucial to an integrated strategy for protecting and restoring foxtail and other white pines [40,71,84]. Breeding programs for blister rust-resistant foxtail pines are being implemented [99]. Other damaging bioagents: Foxtail pines are susceptible to mountain pine beetle attacks [107]. Two rare species of Pityophthorus bark beetles may feed primarily on foxtail pine [17]. While contributing to biodiversity, little is known of the impacts of these Pityophthorus bark beetles to foxtail pine. Limber pine dwarf-mistletoe (Arceuthobium cyanocarpum) occasionally infects foxtail pine [50,69,73]. A fungal needle cast (Lophodermium durilabrum) has caused minor damage to northern foxtail pines in the Marble Mountains [72].Climateaffects foxtail pine's elevational range. For most of the period for which tree records are available (~3,500 years), southern foxtail pine has existed above present treeline [62,63]. For example, Vankat [106] found dead stands of foxtail pine above present timberline (10,800- 11,200 feet (3,300-3,400 m)) on the Kern River Watershed in Sequoia-Kings Canyon National Park. These "ghost forests" may be relicts of foxtail pines that died during a period of global warming [56]. Lloyd and Graumlich [63] documented 3 episodes where southern foxtail pine expanded upslope. Although the data are somewhat unclear [55,89], these expansions appear to have occurred during relatively warm, wet periods. Presently, southern foxtail pine is expanding its range both upslope and laterally into subalpine meadows and previously untreed east slopes. This expansion has been explained as a response to global warming [62,64], or due to a combination of factors including global warming, low conifer diversity (and consequent lack of growth interference for foxtail pine in the upper elevations of the southern Sierra Nevada), and stochasticity [68,82,88].Northern foxtail pine is threatened by global warming. Already restricted to a relatively few high-elevation peaks, there are no higher-elevation refugia for the Klamath Mountains subspecies to migrate to. Many northern foxtail pine populations are being "squeezed off the tops of mountains that are insufficiently high to provide suitable habitat" [77].

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

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Relevance to Humans and Ecosystems

Benefits

Importance to Livestock and Wildlife

Foxtail pine boughs probably provide shelter for wildlife. Chipmunks and birds probably eat the seeds, but little is known about wildlife use of foxtail pine habitats. Research is needed on the ecology of foxtail pine communities.

Palatability/nutritional value: Foxtail pine seeds are palatable and nutritious, but they are not large compared to most 5-needle pines [98]:

82. Ryerson, A. Diane. 1983. Population structure of Pinus balfouriana Grev. & Balf. along the margins of its distribution area in the Sierran and Klamath regions of California. Sacramento, CA: California State University. 197 p. Thesis. [48204]

Contents

P. balfouriana is a tree to 10–20 m (33–66 ft) tall, exceptionally 35 m (115 ft), and up to 2 m (7 ft) in trunk diameter. Its leaves are needle-like, in bundles of five (or sometimes four, in the southern Sierra) with a semi-persistent basal sheath, and 2–4 cm (0.8–1.6 in) long, deep glossy green on the outer face, and white on the inner faces; they persist for 10–15 years. The cones are 6–11 cm (2 3⁄8 - 4 5⁄16 in) long, dark purple ripening red-brown, with soft, flexible scales each with a one millimetre central prickle.

It is thought that P. balfouriana can live up to 3000 years in the Sierra Nevada, although the highest currently proven age is 2110 years. In the Klamath Mountains, ages are only known to about 1000 years.

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Pinus balfouriana is the true "foxtail pine." In leaf character it is hardly, if at all, distinguishable from P . longaeva , but its strongly conic-based cones with distinctly shorter-prickled, sunken-centered umbos at once distinguish it from that species.

Plants shown to be genetically distinct from the type (differences in chemistry, form, foliage, cone orientation, and seeds) have been called Pinus balfouriana subsp. austrina R.Mastrogiuseppe & J.Mastrogiuseppe. As in several other species or species complexes in Pinus , however, there is a problem with a character gradient involving related taxa. The evidence presented by D.K. Bailey (1970) and later by R.J. Mastrogiuseppe and J.D. Mastrogiuseppe (1980) could as well be used to indicate that P . balfouriana (with its two infraspecific taxa) and P . longaeva represent a single species of three subspecies or three varieties. The more conservative view of Bailey is followed here.